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The scientific evidence for the transmission of the SARS-CoV-2 virus into the air by different researchers all points in the same direction – that, according to experts, infectious aerosols are the main means of transmitting from person to person.
Not that it is without controversy.
The aerosol transfer of science “is clear, but it is not accepted in many circles,” said Trisha Greenhalgh, PhD Medscape Medical News.
“In particular, some in the evidence-based medicine movement and some infectious disease clinicians are remarkably resistant to the evidence,” added Greenhalgh, a professor of primary care health sciences at the University of Oxford, Oxford, UK.
“It’s very difficult to see why this is going on,” Greenhalgh said.
“The scientific evidence on the distribution of aerosols in the near field and in the far field has been clear since the pandemic, but there has been resistance to acknowledging it in some circles, including medical journals,” said Joseph G. Allen, DSc, MPH , tell Medscape Medical News when asked to comment.
“This is the week that the dam broke. Three new comments appear in top medical journals – BMJ, The Lancet, JAMA “Everyone makes the same point that aerosols are the dominant mode of transmission,” added Allen, an associate professor of exposure assessment at the Harvard TH Chan School of Public Health in Boston, Massachusetts.
Greenhalgh and colleagues point to an increase in COVID-19 cases in the aftermath of so-called “super-spreader” events, spread of SARS-CoV-2 to people across different hotel rooms, and the relatively lower transmission observed to outdoor events .
Top 10 reasons
They set out ten scientific reasons in support of the distribution of the air in a comment published online on April 15 The Lancet:
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The dominance of transmissions in the air is supported by long-range transmission observed during super-distributors.
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Long-distance transmission has been reported among rooms in COVID-19 quarantine hotels, institutions where infected people have never spent time in the same room.
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Asymptomatic individuals are responsible for approximately 33% to 59% of SARS-CoV-2 transmission and can spread the virus by talking, producing thousands of aerosol particles and a few large droplets.
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Shipping outside and in well-ventilated indoor spaces is lower than in enclosed spaces.
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Nosocomial infections are reported in healthcare settings, where protective measures address large droplets but not aerosols.
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Viable SARS-CoV-2 was detected in the air of hospital rooms and in the car of an infected person.
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Investigators found SARS-CoV-2 in air filters and hospital buildings.
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It’s not just humans – infected animals can infect animals in other cages that are only connected by an air duct.
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No strong evidence refutes the transmission in the air, and contact detection supports secondary transmission in pressurized, poorly ventilated indoor spaces.
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Only limited evidence supports other modes of SARS-CoV-2 transmission, including by fomites or large droplets.
‘We thought we would summarize [the evidence] to clear up the arguments up and down. “We looked hard at evidence but found none,” Greenhalgh said.
“While other routes may make a contribution, we believe the air route is likely to be dominant,” the authors note.
Evidence of the transmission by air was there very early, but the Centers for Disease Control & Prevention, World Health Organization (WHO), and others, reiterated the message that droplets and fomites were primarily concerned.
Response to a review
The top 10 list is also part of the refutation of a systematic review funded by the WHO and published last month, which shows unconvincing evidence for air transmission. The researchers involved in the review say that ‘the lack of recyclable viral culture samples from SARS-CoV-2 prevents firm conclusions from being drawn about airborne transmission.’
However, Greenhalgh and colleagues note that “this conclusion, and the wide distribution of the findings of the review, relate to the effects of human health.”
The current authors also argue that there is already enough evidence about air shipment. “Policy needs to change. We do not need more research on this topic; we need other policies,” Greenhalgh said. “We need front and center ventilation, air filtration if needed, and better fitted masks worn indoors.”
Allen agreed that leadership did not always keep pace with science. “With all the new evidence gathered on the land transmission since last winter, there is still great confusion in the public about the transmission methods,” he said. Allen also serves as commissioner of The Lancet COVID-19 Commission and is chair of the Task Force on Safe Work, Safe Schools, and Safe Travel of the commission.
“It was only last week that CDC withdrew the lead on ‘deep cleaning’ and instead said correctly that the risk of touching surfaces is low,” he added. “Science has been clear on this for more than a year, but official guidance has only recently been updated.”
As a result, many companies and organizations have continued to focus on ‘hygiene theater,’ “Allen said,” to waste resources on cleaning surfaces. Amazingly, many schools include a full day each week for deep cleaning and some library books. quarantine. message that shared air is the problem, not shared surfaces, is a message that needs to be reinforced. “
The National Institute for Health Research, Economic and Social Research Council and Wellcome support Greenhalgh’s research. Greenhalgh and Allen had no relevant financial relationships to disclose.
Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology and critical care. Follow Damian on Twitter: @MedReporter.
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